The present invention relates to calculators for calculating check digits which are obtained from code numbers, and more particularly the invention relates to a check digit calculator capable of obtaining the desired check digits according to a modulus 10 and modulus 11 check, respectively, through a mechanical operation.
Generally, a check digit is a number calculated from the numerical value of each code number, and it is affixed to the least significant digit of the code number for the purpose of automatically detecting a coding error. In other words, a check digit is appended to an important key number such as an account number or customer code number so as to prevent the occurrence of an error such as a wrong account number. The known methods of calculating check digits include a modulus 10 check represented by the Luhn's check and adapted to use various combinations of weights as well as a modulus 11 check, 9' check, 7' check, etc., which similarly use various combinations of weights.
In the past, a check digit has been calculated from each code number in accordance with a predetermined calculating formula by using predetermined weights, and it has been necessary to perform arithmetic operations on each of the digits in each code number, thus requiring much time and labor for the calculation of the check digit. Of course, it is possible to program or enter a check digit computing process into a computer so that the printing of each code number is accompanied by the printing of an associated check digit. However, the use of a computer system only for the purpose of calculating check digits has a great economic demerit and there is a very limited possibility of its practical use.